Search

In this work, the new hydrophobic deep eutectic solvents (HDESs) based on 2-hexyldecanoic acid (HDA) as a hydrogen bond donor (HBD) were used to selectively enrich trace Th from radioactive waste leach solution. These HDESs are characterized by low toxicity, bio-friendliness, low viscosity and sufficient hydrophobicity. Compared with Al, Mg, Ca and RE, HDESs exhibited exceptional selectivity for Th extraction, along with high loading capacity, easy stripping and stable reusability. The mechanism of Th extraction by the HDES is a cation exchange reaction. Based on the thymol (TL):HDA (1:3) HDES, a short flow closed-loop recovery process of Th in the leach solution of radioactive waste residue was developed. After a single-step extraction, the extraction percentage (E%) of Th exceeded 98.0%, while the E% of other elements was less than 0.14%. After stripping, the concentration of Th in the concentrated solution reached 2.16 × 103 mg/L with a purity of 74.2%, which could be directly used for subsequent purification. By adjusting the pH to 4.00, the raffinate was used as a feed solution for RE elements recovery. The HDES-based extraction strategy for Th is simple, safe, efficient and environmentally friendly, providing a new idea for the recovery of radioactive waste residues. [Display omitted] • HDESs based on 2-hexyldecanoic acid were prepared and characterized. • The separation factor between Th and rare earths is much greater than 1000. • A closed-loop thorium recovery process based on HDES was developed. • The extraction percentage of Th by HDES is more than 98%. [ABSTRACT FROM AUTHOR]

[Display omitted] • HDESs were used for removing Al impurity to produce high-purity GdCl 3. • The separation factor of Al/Gd extracted by the HDES is higher than 400. • No emulsification and third phase formation after HDES extraction of Al. • High purity of GdCl 3 products was obtained by HDES extraction system. • HDESs can be easily stripped and remains stable after 5 cycles. In the current industrial production of high-purity gadolinium (Gd) products, aluminum (Al) is enriched into GdCl 3 solution as the main impurity element. It is urgent to develop a new process to effectively remove Al3+ from GdCl 3 solution. In this paper, a novel strategy for separating Al3+ and Gd3+ based on hydrophobic deep eutectic solvent (HDES) is reported. The main physical properties of HDESs were characterized, including density (<0.90 g/cm3), viscosity (<30 mPa·s), water content (<3.5 %) and water solubility (TOC < 300 mg/L). The extraction performances of HDESs for separating of Al3+ from GdCl 3 solution were systemically investigated. Compared with other HDESs, N,N-diethyldodecanamide (DM):ibuprofen (BF) (3:1) HDES has a better separation performance, with the maximum separation factor of Al/Gd (β Al/Gd) being greater than 400. It was found that DM:BF (3:1) HDES could quantitatively remove Al3+ (E% > 99 %) from the original GdCl 3 solution (853.9 mg/L Al3+ and 5466.2 mg/L Gd3+) in three continuous counter-current extraction stages. The co-extraction rate of Gd3+ was only 2.43 %, and the purity of GdCl 3 in the raffinate was 99.9 %. After the loaded HDES was scrubbed one more time, the comprehensive yield of Gd exceeded 99 %. The loaded HDES could be easily stripped, regenerated and sustained stability over five regeneration cycles. The HDES studied in this paper has the advantages of simple preparation, low toxicity, low viscosity, good hydrophobicity and excellent separation effect, which is conducive to the sustainable preparation of high-purity GdCl 3. [ABSTRACT FROM AUTHOR]